Antigenic cell surface modulation associated with malignant transformation will be investigated in order to obtain a clear distinction between the normal, preneoplastic and neoplastic mammary epithelial cells. Initial studies on the cell surface components of normal and tumor mammary epithelial cells have established that the normal mammary cell surface membrane has an additional component which can be radiolabeled with either fucose or iodine. Further research will be aimed towards characterization of the antigenic structure of normal and tumor cell surfaces. Xenogenic antibodies have been prepared to normal mammary epithelial cell-specific antigens and to viral-associated antigens. Syngenic antibodies to mammary tumors (from tumor-bearing animals) have also been isolated. After appropriate absorptions, these antibodies will be used in immunofluorescence studies to determine the presence and location of the respective antigens and the interrelationship with other normal cell surface antigens (i.e. H-2, Thy. 1). In addition, these specific antibodies to normal and tumor-associated antigens will be utilized in radioimmunoprecipitation experiments followed by gel electrophoresis to characterize the respective antigens. Both the qualitative and quantitative differences in cell surface structure of normal and tumor mammary epithelial cells will be defined. Preneoplastic (HAN) epithelial cells will be compared to both normal and tumor mammary epithelial cells in order to assess early events in cell surface modulation accompanying the preneoplastic state.